The present invention relates generally to electrical switches and more particularly to snap action, sump pump switches.
A sump is a pit or well in which liquids collect. The rise and fall of liquid in sumps occurs at unpredictable rates.
A sump pump is commonly used to regulate the amount of liquid which collects within a sump. Specifically, a sump pump can be used to decrease the amount of liquid which accumulates within a sump.
It should be noted that a sump pump may be manually activated, as deemed necessary by the operator, in order to decrease the amount of liquid which accumulates within a sump. However, the manual activation of a sump pump can be very labor intensive, which is highly undesirable.
As a result, sump pump switches (also commonly referred to as float switches) are well known and widely used in the art to control the activation of a sump pump motor in response to the rise and fall of the amount of liquid which collects within a sump. Sump pump switches commonly use a float to monitor the level of liquid which accumulates within the sump. The float, in turn, is connected to a pivotally mounted, switch operating lever. The switch operating lever draws electrical contacts into and out of engagement so as to selectively power the sump pump motor, as will be described further in detail below.
A snap action sump pump switch (also commonly referred to as an over-center spring sump pump switch) is one well-known type of sump pump switch. In a snap action sump pump switch, the switch opening and closing movements, quite desirably, occur with a defined snap. The provision of snap action switching minimizes arcing conditions between the contacts and thereby prolongs switch life, which is highly desirable.
In U.S. Pat. No. 4,196,325 to S. A. Povilatis, there is disclosed a snap action sump pump switch (hereinafter referred to as the Povilatis switch) which selectively connects a power source with a sump pump motor. The Povilatis switch includes a housing which is constructed of a molded, electrically insulated plastic. The housing is shaped to define an interior space, or depression, into which the various switch components are disposed. Such components include a pair of terminal members which are fixedly mounted onto the housing and which are externally accessible for connection to the power source. A pair of contact members are fixedly mounted onto the housing and are electrically connected to the sump pump motor, such as through a pair of insulated, flexible electrical wires. A generally U-shaped, electrically insulated contact bridge, or yoke, is pivotally disposed within the interior space of the housing. A pair of electrically conductive movable contacts are pivotally mounted onto parallel extending, spaced apart arms of the yoke and are capable of relative lateral movement. An over-center mechanism is provided to pivotally move the yoke (and, as a consequence, the movable contacts mounted on the yoke) between two positions. The over-center mechanism includes an actuator arm, or operating lever, which is pivotally mounted onto the housing. A pivot bushing and a coiled spring together serve to connect one end of the actuator arm to the yoke.
It should be noted that each of the pair of electrically conductive movable contacts is drawn in continuous contact with an associated, electrically conductive, terminal member, thereby establishing an electrical current path between each terminal member and its corresponding movable contact. Specifically, each movable contact includes a pair of oppositely disposed, outwardly projecting tabs on side edges of a rear end portion thereof. The pair of tabs on each movable contact align in contact within a pair of triangularly shaped, rearwardly opening notches formed in the rear edge portions of its associated terminal member. The notches on each terminal member serve as a fulcrum about which its associated movable contact reciprocally pivots thereagainst when actuated between first and second switch positions.
In use, the Povilatis switch functions in the following manner to control the activation of a sump pump. The terminal members of the switch are electrically connected to the power source and the contact members of the switch are electrically connected to the sump pump. A float is mounted onto the free end of the actuating arm and remains on the top surface of the liquid accumulating in the sump.
Once the surface of the liquid rises to a predetermined level, the float pivots the actuating arm in such a manner so that the over-center mechanism pivots the yoke, thereby drawing the movable contacts mounted on the yoke into electrical engagement with the fixed contacts. The electrical engagement between the movable contacts and the fixed contacts establishes a current path from the power source, through the terminal members, through the movable contacts, through the fixed contact members and into the sump pump motor, thereby energizing and activating the sump pump motor.
To the contrary, as the surface of the liquid falls, the float pivots the actuating arm in the opposite direction so that the over-center mechanism, in turn, pivots the yoke in the opposite direction, thereby disengaging the movable contacts from electrical contact with the fixed contacts. The electrical disengagement between the movable contacts and the fixed contacts opens the current path between the source of power and the sump pump motor, thereby de-activating the sump pump motor.
Although well-known and widely used in commerce, the Povilatis switch suffers from a notable drawback in its design. Specifically, with the Povilatis switch disposed in either its closed position or its open position, a current path is established between the electrical terminal members and the movable contacts through the four movable contact pivot points. As noted above, each movable contact includes a pair of oppositely disposed, outwardly projecting tabs on side edges of a rear end portion thereof. The pair of tabs on each movable contact align in contact within a pair of triangularly shaped, rearwardly opening notches formed in the rear edge portions of its associated terminal member. The notches on each terminal member serve as a fulcrum about which its associated movable contact reciprocally pivots thereagainst when actuated between first and second switch positions. As can be appreciated, the fact that electrical current is required to travel through pivot points, renders the Povilatis switch susceptible to many undesirable conditions which can decrease the life of the switch.
For example, the fact that electrical current is required to travel through the pivot points renders the switch susceptible to connection problems between each movable contact and its associated terminal member due to manufacturing tolerances in said components (e.g., burrs on the stamped parts), which is highly undesirable.
As another example, the fact that large amounts of electrical current are required to travel through the pivot points renders the switch susceptible to arcing conditions between the movable contacts and the electrical terminal members, which is highly undesirable. In fact, arcing conditions can wear the quality of the connection through the pivot points. As arcing in the pivot points deteriorates integrity of the connection, the contacts can become misaligned, thereby causing the switch ultimately lock up, or fail, which is highly undesirable.
It is an object of the present invention to provide a new and improved sump pump switch for controlling the starting and stopping of a sump pump motor in response to the rise and fall of the level of a liquid collecting in a sump.
It is another object of the present invention to provide a sump pump switch as described above which is of the snap action variety.
It is yet another object of the present invention to provide a sump pump switch as described above which does not require electrical current to travel through one or more pivot points.
It is still another object of the present invention to provide a sump pump switch as described above which is insusceptible to arcing conditions.
It is yet still another object of the present invention to provide a sump pump switch as described above may be mass produced, has a minimal number of parts, and can be easily assembled.
Accordingly, in one embodiment of the present invention, there is provided an electric switch comprising an electrically insulated housing, an electrically conductive terminal member disposed within said housing, an electrically conductive contact member disposed within said housing, an electrically conductive movable contact disposed in continuous pivotal contact with said terminal member, said movable contact selectively contacting said contact member, and an electrically conductive wiper contact disposed within said housing, said wiper contact being connected to said terminal member and to said movable contact.
Additional objects, as well as features and advantages, of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description or may be learned by practice of the invention. In the description, reference is made to the accompanying drawings which form a part thereof and in which is shown by way of illustration specific embodiments for practicing the invention. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.